This invention relates to tools used in adjusting the color balance on a color television receiver and, more particularly, the color bar pattern matching devices.
The reproduction of accurate color balance upon a color television receiver is a desirable feature. Color balance or accurate color reproduction becomes a necessity in closed circuit commercial television systems. For example, physicians need precise color reproduction in order to make accurate evaluation. Numerous other instances in which accurate color reproduction in closed circuit systems can be easily imagined. In settings where the cost of maintenance can be critical, as in hospitals and research facilities, it is also important that the devices used to adjust a color receiver and/or monitor be economical. If such devices enable someone who is not a trained service person to make the adjustments, the device is of even more importance.
Until now, it was believed that a device which is both economical and so easy to use that a trained technician is not required was not available. Color adjustments may be made by displaying predetermined color patterns on the receiver and/or monitor screen. Frequently, these color patterns take the form of horizontal color bars having a predetermined color pattern. The thickness of each color bar pattern is also of predetermined dimensions for each size television screen.
The color bar pattern may be generated by a color bar generator. However, in closed circuit systems, the pattern is frequently provided by a prerecorded magnetic tape.
One device for use of adjusting color on a receiver comprises a cardboard card, upon which the colors are printed in opaque inks. The technician adjusts the receiver by comparing the displayed color against the hand-held card. This device requires that the colors on the cards be accurately printed and that the dyes will not fade over a period of time. Obviously, these factors of time and the exposure of the card to ambient light will render the card inaccurate within a very short time.
Another device has been suggested by Davis et al., in U.S. Pat. No. 2,931,856. Davis et al. provides a series of translucent color bars to be placed over the entire screen of a television receiver. The receiver must have, surrounding the screen, a light which provides proper color temperature illumination for that portion of the mask which is outside the screen area. A color bar pattern is then generated upon the screen and viewed through the translucent bars. The illuminated color is matched against the color bars displayed on the screen, as viewed through the mask. When the colors are matched, Davis et al. suggests that the color receiver has been accurately adjusted. However, this device has a number of serious disadvantages. First of all, in order to be operative, the television receiver must be provided with a light immediately adjacent the screen and so disposed as to illuminate the mask from behind. It is believed that such receivers are no longer available. Most important, however, is the fact that this device requires that the color bars on the screen be matched with the color bars of the surrounding lighting element. If the color of the lighting element is somewhat distorted (i.e., is not a pure white light), the compared colors will be inaccurate, in the same way as if someone held up a card of pre-printed colors and compared it against the screen and attempted to align the color bars displayed on the TV receiver with that on the pre-printed card. Further, as the surrounding lighting element ages, it is well known that its color temperature changes, as well.